1. Field of the Invention
The invention is based on a circuit arrangement and a method for adjusting the power consumption of a load, in particular of a cooling fan motor of a motor vehicle, that can be operated by a direct-voltage system.
2. Description of the Prior Art
German Patent Disclosure DE 100 44 388 A discloses a circuit arrangement for turning a high-powered direct-current motor on and off, which motor can be operated by the on-board electrical system of a motor vehicle. The circuit is connectable to the direct-current system via a semiconductor switch with an associated control unit. For thermal relief of the semiconductor switch after the actuation current has faded, the semiconductor switch is bridged by a relay contact. With the known arrangement, it is not possible to detect and monitor the motor current.
From German Patent DE 196 48 710 C, a circuit arrangement is also known which connects an electric motor of the cooling fan of an internal combustion engine directly to the current supply, on the one hand via a current path with a series resistor and on the other via a current path without a series resistor, for two-stage triggering of the electric motor at different rotary speeds. The switchover of the triggering is effected by means of a control unit, which connects the electric motor to the voltage source via one of the two lead lines. In addition, a microtemperature fuse is disposed in the current circuit with the series resistor and if the current rises impermissibly high, this fuse interrupts this current circuit via the series resistor. The control unit for the switchover of the current paths does not receive any feedback about the magnitude at the time of the supply current for the electric motor.